Abstract

We propose and demonstrate a new method to generate a dark hollow beam (DHB) and amplify it simultaneously by a liquid-core optical fiber (LCOF) filled with CS2. A DHB with an adjustable dark spot size (DSS) is simply obtained by changing the incident angle of the laser beam. Based on non-collinear Brillouin amplification, a weak DHB can be amplified with high gain. The amplification factor of 106 is achieved for a DHB of 4pJ. This DHB should have promising applications in many fields due to its compact structure, low cost, wide adjustment range of the DSS, and wide operating wavelength.

Spot images of amplifier output (a), (c) with the pump off and (b), (d) with the pump on. (a), (b): the incident angles of the pump and signal are all 0°; (c), (d): the incident angles of the pump and signal are 9° and 6°, respectively.